When an electronic apparatus, such as a notebook computer, portable TV, cell phone or PDA, is operated, parts of the electronic apparatus, such as a power source line, a conducting wire or an electronic component of the electronic apparatus, generate electromagnetic waves, and the signal noise due to the electromagnetic waves can interfere with the operation of other electronic components in the electronic apparatus. This mechanism is called electromagnetic interference (EMI).
With developments in electronic technology, signal transmitting speed has continuously increased to obtain better performance. For example, to enhance the performance of a liquid crystal display (LCD) the signal transmitting speed has to be accelerated. However, this causes serious EMI problems due to the electromagnetic noise being radiated from the signal wires of the LCD. In addition, the main design trend for electronic apparatuses has been in miniaturizing, worsening the EMI problems due to the decreasing distance between each of the electronic components located in the electronic apparatus. For example, a broadband noise generated by a switching power supply circuit can seriously interfere with the performance of the LCD when the switching power supply circuit is not distanced far enough away from the signal wires of the LCD.
To resolve the problems, a ferrite core has been provided that is put around the signal wires to eliminate their electromagnetic noise. Another method for resolving the problems is to wrap the signal wires in a conductive cloth for isolating the signal wires from other components, wherein a grounding pigtail electrically connected to the conductive cloth is also provided to reduce the EMI of the signal wires.
However, the use of the ferrite core in an electronic apparatus increases the weight of the electronic apparatus, restricts the space for electrical wiring, and requires more material cost. Furthermore, since securing the ferrite core in the apparatus is difficult, other components in the apparatus can be crushed by the unfixed ferrite core when the electronic apparatus is transported. Moreover, the use of the conductive cloth and the pigtail can merely eliminate the electromagnetic waves radiated from the signal wires but cannot also eliminate the electromagnetic waves radiated from the power supply line.
It is desirable to provide a cheaper EMI shielding and grounding structure for not only shielding an electronic component from EMI but also for eliminating the electromagnetic waves radiated from the component which is shielded.